Kinetics of electron transfer will be investigated, in order to elucidate fast and slow oxidation-reduction reactivities which prevail in various hemoproteins. "Bioelectrochemical modelling" will be used to study the mechanism by which heme-iron is converted from the ferrous to the ferric state and vice-versa. The sluggish redox properties of hemoglobin and myoglobin on the one hand, and the rapid electron transfer behavior of cytochrome c on the other hand, will be mimicked in model compounds synthesized ad-hoc. Relevant electrooxidation-reduction rates will be determined by polarography, cyclic voltammetry, and by potentiostatic, galvanostatic and coulostatic relaxation methods. Corresponding thermochemical information will be obtained with the aid of titration calorimetry.